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Biotechnology Glossary R-Z


Race A distinguishable group of organisms of a particular species. Criteria for distinctness can be one or a combination of geographic, ecological, physiological, morphological, genetic and karyotypic factors.

Radioimmunoassay (Abbreviation: RIA). An assay based on the use of a radioactively labelled antibody, where the amount of radiation detected indicates the amount of target substance present in the sample.

Receptor A trans-membrane protein located in the plasma membrane that can bind with a ligand on the extracellular surface, as a result of which it induces a change in activity on the cytoplasmic surface. More generally, a site in a molecule that allows the binding of a ligand.

Recessive Describing an allele whose effect with respect to a particular trait is not evident in heterozygotes.

Recessive allele Allelic state of a gene, where homozygosity is required for the expression of the relevant phenotype.

Recessive genetic disorder A disorder which occurs only if there are two copies of a defective gene present in the genome. Genes are present in pairs, one from each parent. Individuals with a recessive genetic disorder inherit two defective genes from their parents. Cystic fibrosis is an example of a recessive genetic disorder.

Recombinant A term used in both classical and molecular genetics. 1. In classical genetics: An organism or cell that is the result of meiotic recombination. 2. In molecular genetics: A hybrid molecule made up of DNA obtained from different organisms. Typically used as an adjective, e.g. recombinant DNA.

Recombinant DNA The result of combining DNA fragments from different sources.

Recombinant DNA technology A set of techniques for manipulating DNA, including: the identification and cloning of genes; the study of the expression of cloned genes; and the production of large quantities of gene product.

Regeneration The growth of new tissues or organs to replace those injured or lost. In planttissue culture, regeneration refers to the development of organs or plantlets from an explant.

Regulations Regulations are a form of law, often referred to as delegated or subordinate legislation. They have the same binding legal effect as Acts and usually state rules that apply generally, rather than to specific persons or things. However, regulations are not made by Parliament. Rather, they are made by persons or bodies to whom Parliament has delegated the authority to make them, such as the Governor in Council, a minister or an administrative agency. Authority to make regulations must be expressly delegated by an Act. Acts that authorize the making of regulations are called enabling Acts.

Regulatory agency The agency or government department that has responsibility over the legislation (acts and regulations) for a given sector of the government.

Regulatory framework The due process of regulation surrounding a single topic, such as seeds or fertilizers, that entails all of the relevant legislative documents (acts, regulations, annexes) and describes the federal agency responsible for administering the framework.

Regulatory gene A gene with the primary function of controlling the rate of synthesis of the products of one or several other genes or pathways.

Renewable resource A natural resource that can be replenished by natural means at rates comparable to its rate of consumption.

Replication The in vivo synthesis of double-stranded DNA by copying from a single-stranded template.

Repressible gene A gene whose expression can be diminished or extinguished by the presence of a regulatory molecule.

Repression Inhibition of transcription by preventing RNA polymerase from binding to the transcription initiation site.

Resorption The break down of minerals from structures in the body. For example, the dissolution of calcium from bones.

Restenosis Recurrent narrowing of a heart valve or artery after corrective surgery.

Restriction endonuclease A class of enzymes that cut DNA after recognizing a specific sequence. The three types of restriction endonuclease are: I. Where the cut occurs within a random sequence at sites >1kbp from the recognition sequence, and has both restriction and methylation activities. II: Cuts within, or near a short, usually palindromic recognition sequence. A separate enzyme methylates the same recognition sequence. III: Cuts 24-26bp downstream from a short, asymmetrical recognition sequence, requires ATP and has both restriction and methylation activities. Type II enzymes are the class used for most molecular biology applications.

Restriction enzyme Synonym of restriction endonuclease.

Restriction fragment length polymorphism (Abbreviation: RFLP). A class of genetic marker based on the detection of variation in the length of restriction fragments generated when DNA is treated with restriction endonucleases. Differences in fragment lengths arise due to genetic variation with respect to the presence or absence of specific recognition site(s). RFLPs were initially detected by Southern hybridization but are now detected by electrophoresis of digested PCR product.

Retrovirus A class of eukaryotic RNA viruses that, by using reverse transcription, can form double-stranded DNA copies of their genomes, which can integrate into the chromosomes of an infected cell. Pathogenic retroviruses include HIV and the causative agents of many vertebrate animal cancers.

Retting A biological process that removes gums and stem tissue from soft fibers, in the processing of natural fibers. It is carried out in water, dew, or snow through the action of certain groups of bacteria and fungi.

Rheumatoid arthritis A form of arthritis that attacks the connective tissues lining the joints.

Ribonuclease (Abbreviation: RNAse). Any enzyme that catalyses the hydrolysis of RNA.

Ribonucleic acid (Abbreviation: RNA). An organic acid polymer composed of adenosine, guanosine, cytidine and uridine ribonucleotides. The genetic material of some viruses, but more generally is the molecule, derived from DNA by transcription, that either carries information (messenger RNA), provides sub-cellular structure (ribosomal RNA), transports amino acids (transfer RNA), or facilitates the biochemical modification of itself or other RNA molecules.

Ribose A monosaccharide found in all ribonucleosides, ribonucleotides and RNA. Its close analogue, 2-deoxyribose, is similarly found in all deoxyribonucleosides, deoxyribonucleotides and DNA.

Ribosomal DNA The coding locus for ribosomal RNA. This is generally a large and complex locus, typically composed of a large number of repeat units, separated from one another by the intergenic spacer. A repeat unit comprises a gene copy for each individual ribosomal RNA component, separated from one another by the internal transcribed spacer.

Ribosomal RNA (Abbreviation: rRNA). The RNA molecules that are essential structural and functional components of ribosomes, where protein synthesis occurs. Different classes of rRNA molecule are identified by their sedimentation (S) values. E. coli ribosomes contain one 16S rRNA molecule (1541 nucleotides long) in one (small) ribosomal sub-unit, and a 23S rRNA (2904 nucleotides) and a 5S rRNA (120 nucleotides) in the other (large) sub-unit. These three rRNA molecules are synthesized as part of a large precursor molecule which also contains the sequences of a number of tRNAs. Special processing enzymes cleave this large precursor to generate the functional molecules. Constitutes about 80% of total cellular RNA.

Ribosome The sub-cellular structure that contains both RNA and protein molecules and is the site for the translation of mRNA into protein. Ribosomes comprise large and small sub-units.

Roslin technique A type of nuclear transfer used to clone mammals. It fuses a donor cell and an egg cell together and induces it to grow into an embryo by using electrical pulses.


S phase The phase in the cell cycle during which DNA synthesis occurs.

Salmonella A genus of rod-shaped, Gram-negative bacteria that are a common cause of food poisoning.

Saturated fats/fatty acid A kind of fat often found in meat and dairy products, as well as some vegetable oils, such as coconut and palm oils. These fats contain single bonds and cannot incorporate any additional hydrogen atoms. They are associated with high cholesterol levels in the blood.

Seed Botanically, the matured ovule without accessory parts. Colloquially, anything which may be sown; i.e. seed potatoes (which are vegetative tubers); seed of wheat (karyopses) etc.

Selectable Having a gene product that, when present, enables the identification and preferential propagation of a particular genotype.

Selectable marker A gene whose expression allows the identification of a specific trait or gene in an organism.

Selection 1.Differential survival and reproduction of phenotypes. 2. A system for either isolating or identifying specific genotypes in a mixed population.

Selection pressure The intensity of selection acting on a population of organisms or on cells in culture. Its effectiveness is measured in terms of differential survival and reproduction, and consequently in changes in allele frequency in a population.

Selective breeding The breeding of animals or plants that have desirable characteristics. Also known as conventional or traditional breeding.

Senescence A late stage in the development of multicellular organisms, during which irreversible loss of function and degradation of biological components occur. The physiological ageing process in which cells and tissues deteriorate and finally die.

Sequence The linear order of nucleotides along a DNA or RNA molecule, and the process of obtaining this. Genome sequencing aims to generate the linear order of all nucleotides present in the nuclear DNA of an organism.

Serum Blood plasma that has had its clotting factor removed.

Sex chromosome Differentiated chromosome which is responsible for the determination of sex of the individual. For all mammals, a small number of flowering plants and many insects, female individuals carry a pair of X chromosomes, and males carry one X and one Y. For birds, reptiles and most amphibians, male individuals carry a pair of W chromosomes, and females carry one W and one Z. In some insects there is only one sex chromosome, X, and sex is determined by the number of these present.

Sex-influenced dominance The tendency for gene action to vary between the sexes within a species. For example, the presence of horns in some breeds of sheep appears to be dominant in males but recessive in females.

Single-stranded DNA (Abbreviation: ssDNA). DNA molecules separated from their complementary strand, either by its absence or following denaturation.

Site-specific mutagenesis The induction of mutations, by molecular biology techniques, in one or more specific nucleotides within a defined coding sequence in order to create altered forms of the gene product. Used to define the active sites of proteins and for protein engineering.

Soluble fibre Soluble fibre dissolves in the gut and forms a viscous gel that slows down the release of some nutrients. It can also reduce the risk of heart disease, by reducing blood cholesterol levels. Soluble fibre is present in fruit, vegetables, pulses (e.g. kidney beans, baked beans, lentils) and foods containing oats, barley or rye.

Somatic cell Cells not involved in sexual reproduction, i.e. not germ cells.

Somatic corn embryos Somatic cells of corn. Also see Somatic cells.

Southern blot A nitrocellulose or nylon membrane to which DNA fragments previously separated by gel electrophoresis, have been transferred by capillary action.

Speciation The evolutionary differentiation of a pre-existing species into one or more distinct species.

Species A class of individuals capable of interbreeding, but which is reproductively isolated from other such groups having many characteristics in common. A somewhat arbitrary and sometimes blurred classification; but still quite useful in many situations.

Splicing 1. During the maturation of eukaryotic mRNA, the process that removes intron sequences and covalently joins exon sequences. Synonym: editing. 2. In recombinant DNA technology, the term refers to the ligation of two fragments of DNA together.

Sponsor(s) An individual, corporate body, institution, or organization that conducts a clinical trial.

Spore 1. A reproductive cell that develops into an individual without union with other cells; some spores such as meiospores are the product of the germ line, but others are asexual in nature. 2. A small, protected resting body, often synthesized by micro-organisms when nutrient levels are low.

Standards Standards are defined by the International Organization of Standardization (ISO) as “documented agreements containing technical specifications or other precise criteria to be used consistently as rules, guidelines or definitions of characteristics, to ensure that materials, products, processes and services are fit for their purpose.”

Start codon The codon which specifies the first amino acid of a polypeptide chain and at which the ribosome starts the process of translation. In bacteria, this is either AUG (translated as n-formyl methionine) or, rarely, GUG (valine). In eukaryotes, it is always AUG and is translated as methionine. The start codon sets the reading frame for translation.

Stem cell An undifferentiated somatic cell that is capable of either division to give rise to daughter stem cells, or differentiating into any specialized cell type given the appropriate signals. Cultured stem cells are critical to the concept of therapeutic cloning.

Stop codon A set of three nucleotides for which there is no corresponding tRNA molecule to insert an amino acid into the polypeptide chain. Protein synthesis is hence terminated and the completed polypeptide released from the ribosome. Three stop codons are known: UAA (ochre), UAG (amber) and UGA (opal).

Substantially equivalent The equivalence of a particular organism, in terms of its specific use and safety to the environment and human health, to those of that same species that are in use and generally considered as safe in Canada, based on valid scientific rationale.

Substrate 1. A compound that is altered by an enzyme. 2. Food source for growing cells or micro-organisms. 3. Material on which a sedentary organism lives and grows.

Sub-unit vaccine One or more immunogenic proteins, either purified from the pathogen itself or produced from a cloned pathogen gene. A vaccine composed of a purified antigenic determinant that is separated from the virulent organism.

Subunit preparation The preparation of a subunit vaccine – a vaccine composed primarily of virus or other microorganism proteins that cannot cause disease.

Summer-fallowing (To fallow) To leave a field unseeded for a period of time after plowing, in order to recover natural fertility.

Suppressor mutation A mutation that reverses the effect of an earlier mutation, e.g. a mutation in a gene for a tRNA that permits it to read and override an amber mutation.

Synthase One of the six primary classes of enzymes, composed of those that catalyze the division of carbon or other bonds without a hydrolysis or oxidation reaction.

Synthesis/synthesizing (In DNA molecules) The building of a known sequence of nucleotides into a chain called an oligonucleotide (of which genes are made) or DNA
(In proteins) Chemical synthesis (manufacture) of a known protein molecule.


T cell Lymphocytes which pass through the thymus gland during maturation. Different kinds of T cells play important roles in the immune response. Synonym: T lymphocyte.

T cell receptor An antigen-binding protein, located on the surface of mammalian killer T cells, which mediates the cellular immune response. T cell antigen encoding genes are assembled from gene segments by somatic recombination processes that occur during lymphocyte differentiation.

Taxonomy The theories and techniques of describing, naming, and classifying organisms.

Tay-Sachs disease An inherited disease characterized by severe neurological deterioration and mental and physical retardation.

Telomere The structure found at the end of eukaryotic chromosomes containing specialized repetitive (and widely conserved across species) DNA sequences, which are necessary to assure the completion of a cycle of DNA replication.

Telophase The last stage in each mitotic or meiotic division, in which the chromosomes coalesce at each pole of the dividing cell.

Template An RNA or single-stranded DNA molecule, used by polymerases to generate a complementary nucleotide strand.

Terminator 1. A DNA sequence just downstream of the coding segment of a gene, which is recognized by RNA polymerase as a signal to stop synthesizing mRNA. 2. A term used in GMO technology for a transgenic method which genetically sterilizes the progeny of the planted seed, thereby preventing the use of farm-saved seed.

Testcross A cross between a genetically unknown individual and a recessive tester to determine whether the individual in question is heterozygous or homozygous for a certain allele. It can also used as a method to test for linkage, i.e. to estimate recombination fraction.

Therapeutic cloning The potential use of stem cells to grow, in vitro, tissue or organs for use in transplantation. Because these cells would be obtained from, and would therefore be genetically identical to the patient’s own cells, problems of transplant rejection would be overcome. The technique would also remove the difficulty of identifying an organ donor.

Thymidine The deoxyribonucleoside resulting from the combination of the base thymine (T) and the sugar 2-deoxy-D-ribose.

Thymine (Abbreviation: T). One the bases found in DNA. See: thymidine.

Thymus (gland) An organ at the base of the neck which plays an important role in immune system responses. It produces T-cells which are crucial in identifying self and non-self antigens.

Thyroid gland A gland located at the base of the neck that regulates a person’s metabolic rate through the production and secretion of thyroid hormone.

Tissue A group of cells of similar structure which sometimes performs a special function.

Tissue culture The in vitro culture of cells, tissues or organs in a nutrient medium under sterile conditions.

Toxicity The extent to which a toxic compound negatively affects a given trait.

Toxicological effects The actions of foreign substances in the body, and the quality or degree of these substances being poisonous.

Toxin A compound produced by one organism, which is deleterious to the growth and/or survival of another organism of the same or different species.

Trait One of the many characteristics that define an organism. The phenotype is a description of one or more traits. Synonym: character.

Transcript An RNA molecule that has been synthesized from a specific DNA template. In eukaryotes, the primary transcript produced by RNA polymerase is often processed or modified in order to form functional mRNA, rRNA or tRNA.

Transcription Synthesis of RNA from a DNA template via RNA polymerase.

Transcription factor A protein that regulates the transcription of genes.

Transcription unit A segment of DNA that contains signals for the initiation and termination of transcription, and is transcribed into one RNA molecule.

Transduction 1. Genetic: the transfer by means of a viral vector of a DNA sequence from one cell to another. 2. Signal: any process that helps to produce biological responses to events in the environment (e.g. transduction of hormone binding into cellular events by hormone receptors).

Transformation 1. The uptake and integration of DNA in a cell, in which the introduced DNA is intended to change the phenotype of the recipient organism in a predictable manner. 2. The conversion, by various means, of cultured animal cells from controlled to uncontrolled cell growth, typically through infection with a tumour virus or transfection with an oncogene.

Transformants Cells which have successfully incorporated foreign DNA into their genomes.

Transgenic An individual in which a transgene has been integrated into its genome. In transgenic eukaryotes, the transgene must be transmitted through meiosis to allow its inheritance by the offspring.

Translation The process of polypeptide synthesis in which the amino acid sequence is determined by mRNA, mediated by tRNA molecules, and carried out on ribosomes.

Transplant rejection The rejection of the donor organ, tissue or cell by the transplant recipient’s immune system.

Twin studies Refers to the large-scale study of both fraternal and identical twins, raised together or apart, to determine the environmental and genetic factors involved in a specific development.


Unconfined release The use of a novel organism that is not subject to reproductive and physical isolation from the natural or agricultural environment, site inspections, land use restrictions and/or restricted use of seed or progeny.

Undifferentiated Undifferentiated cells are those which have not been committed to become part of a specialized tissue.

Unicellular Tissues, organs or organisms consisting of a single cell.

Uracil (Abbreviation: U). One the bases found in RNA. See: uridine.

Uridine The (ribo)nucleoside resulting from the combination of the base uracil (U) and the sugar D-ribose.


Vaccine A preparation of dead or attenuated (weakened) pathogens, or of derived antigenic determinants, that can induce the formation of antibodies in a host, and thereby produce host immunity against the pathogen.

Vacuole A fluid-filled membrane-bound cavity inside many plant cells, in which various plant products and by-products are stored.

Variable expressivity Variation in the phenotype caused by different alleles of the same gene and/or by the action of other genes and/or by the action of non-genetic factors.

Variance A statistical term representing a measure of the dispersion of data from the overall mean. Used to quantify the variability of a population.

Variant An individual that is genetically distinct from others in the population.

Variety 1. A naturally occurring subdivision of a species, with distinct morphological characters. 2. A defined strain of a crop plant, selected on the basis of phenotypic (sometimes genotypic) homogeneity.

Vector 1. An organism, usually an insect, that carries and transmits pathogens. 2. A small DNA molecule (plasmid, virus, bacteriophage, artificial or cut DNA molecule) that can be used to deliver DNA into a cell. Vectors must be capable of being replicated and contain cloning sites for the introduction of foreign DNA.

Viability The capability to live and develop normally.

Viral coat protein A protein present in the layer surrounding the nucleic acid core of a virus.

Virulent phage A phage that destroys its host bacterium.

Virus An infectious particle composed of a protein capsule and a nucleic acid core (DNA or RNA), which is dependent on a host organism for replication.


Western blot A technique whereby a complex mixture of size-separated proteins is ixed to a solid support, and then probed with a labelled antibody. Useful, for example, for the measurement of levels of production of a specific protein in a particular tissue or at particular developmental stage.

Wet weight See: fresh weight.

Wetting agent A substance (usually a detergent) that improves the contact of a liquid to a solid surface by reducing its surface tension.

Wild type The most frequent allele or genotype found in nature, or a specified organism against which mutants are defined.

Wobble hypothesis An explanation of how one tRNA may recognize more than one codon. The first two bases of the mRNA codon and anticodon pair properly, but the third base in the anticodon has some flexibility that permits it to pair with either the expected base or an alternative.


X-chromosome See: sex chromosome.

Xenobiotic A chemical compound that is not produced by, and often cannot be degraded by, living organisms.

Xenogeneic Refers to organs, genetically engineered (“humanized”) todecrease the chance of rejection, that have been grown in an animal of another species for potential transplant to humans.

Xenotransplantation The transplantation of tissue or organs from onespecies to another species, typically from pigs to humans.

X-linked The presence of a gene on theX-chromosome.


Yeast A unicellular ascomycete fungus, commonly found as a contaminant in plant tissue culture.

Young’s Syndrome A genetic disorder that affects the hairs, called cilia, that are found in the tubes and ducts of the body. This syndrome results in an inability to produce sperm and chronic respiratory problems in men.


Zone of elongation The section of the young root or shoot just behind the apical meristem, in which the cells are enlarging and elongating rapidly.

Zoo FISH Fluorescence in situ hybridization technique, probing metaphase chromosomes of one species with DNA from another species. The technique allows inferences to be made regarding the evolutionary relationships between species.

Zygote The diploid cell formed by the fusion of two haploid gametes during fertilization in eukaryotic organisms with sexual reproduction.